The present invention relates generally to X-ray generation systems and more specifically to X-ray tubes driven by axial flux motors.
An X-ray tube comprises an electron beam emitted from a cathode to strike an anode target assembly for producing X-rays. The electron beam is accelerated by a potential difference maintained between the cathode and the anode target assembly, typically on the order of about 60 kilovolts to about 140 kilovolts. The accelerated electron beam hits an anode target at a focal spot, generating the X-ray radiation thereby. Typically, only about one percent of the kinetic energy of the electron beam is converted to X-ray radiation. The remaining portion of the kinetic energy of the electron beam is converted to thermal energy. It is desirable to rotate the anode target assembly by a drive arrangement at a desired speed, to avoid local melting of the anode target assembly.
In conventional X-ray generation systems, the X-ray tube anode target assembly is driven by an induction motor, typically a radial flux induction motor. Such X-ray tube having the anode target assembly driven by the radial flux motor is typically characterized by a substantially long axial span caused due to typical mass distribution of the rotating components. Such rotating components include, for example, a rotor of the radial flux machine and the anode target assembly. The bearings supporting the rotating components are thus spaced apart from each other by a substantially long distance. Such bearings experience excess mechanical load, such as static load and dynamic load, due to excess weight and centrifugal force of the rotating components, respectively. Furthermore, the bearings are exposed to a substantial thermal load, generated due to impingement of the electron beam on the anode target assembly. The mechanical load coupled with such thermal load experienced by the bearings poses a challenge to X-ray tube designers, particularly with regard to enhancing the bearing life so as to ensure trouble free operation of the X-ray generation system.
Although certain methods have been used to minimize the thermal load on X-ray tube bearings, issues pertaining to excess static load and dynamic load experienced by the bearings continue to pose a challenge to X-ray tube designers. The typical mass distribution of the rotating components poses additional limitations on design of X-ray generation systems, particularly with regard to minimizing weight and improving overall compactness of the X-ray tube.
Accordingly, there is a need in the art to design an X-ray tube that minimizes static and dynamic load on the bearings to achieve enhanced bearing life, minimize weight of the X-ray generation system and improve system reliability.